The gaseous effluents from the manufacturing of semiconductor materials, devices, products and memory articles involves a wide variety of chemical compounds used and produced in the process facility. These compounds include inorganic and organic compounds, breakdown products of photo-resist and other reagents, and a wide variety of other gases which must be removed from the waste gas streams before being vented from the process facility into the atmosphere. In such systems, process gas, which may be a single component or multi-component composition, is mixed with an oxidant, such as high purity oxygen, air or nitrous oxide, then the resulting gas mixture is oxidized in a reaction chamber.
In semiconductor manufacturing processes, various processing operations can produce combustible gas streams. Hydrogen and a variety of hydride gases such as silane, germane, phosphine, arsine, etc. may be present and, if combined with air, oxygen or other oxidant species such as nitrous oxide, chlorine, fluorine and the like, form combustible mixtures.
However, the composition of the waste gas generated at a work station may vary widely over time as the successive process steps are carried out.
Faced with this variation of the composition of waste gas streams and the need to adequately treat the waste gas on a continuous basis during the operation of the facility, a common approach is to provide a single large scale waste treatment system for an entire process facility, which is over designed in terms of its treatment capacity, which can continuously treat the waste gas. Large scale oxidation units, which often use catalytic chemistry, however, are typically expensive, particularly since they are over designed in terms of treatment capacity, must be heated to an appropriate elevated temperature and often generate a substantial amount of heat. It is difficult to make such gas treatment processes economically viable without recovering a substantial portion of the heat generated.
Accordingly, oxidation beds in large scale, typically single unit catalytic oxidation systems, are greatly oversized relative for the size and scale of oxidation beds which would be otherwise minimally required for treatment of the effluent stream under an average operating conditions, average concentration levels, and average composition of pollutants.
The present invention provides discrete units which may be employed at the point of use, that is, applied to a single tool, individual processing operation, and the like, within a plant facility to effectively and efficiently remove the pollutants without being over designed with respect to volume capacity, heat generation and power consumption.
The present invention provides an apparatus for removing pollutants from gaseous streams which comprises a thermal reactor, a particle removal chamber and a regenerable acid scrubber. The thermal reactor is provided with at least one inlet comprising a conduit terminating with a portion of the conduit within the reactor which projects into the reactor into a tube defining an area in which there is flame formation. The thermal reactor comprises a central chamber accommodating heating elements, a side inlet communicating with an exterior air space between the exterior wall and the heating elements, and an interior air space communicating with the exterior air space. The interior air space is defined by the interior wall and the heating elements, and an orifice in the interior wall is provided for introducing air from the interior space into the central chamber. The gases exiting the thermal reactor are passed through a liquid vortex which cools gases from the reaction chamber.
The gases from the combustion chamber are then passed through a counter-current/co-current flow packed bed for trapping and condensing particles by upwardly flowing the gas stream through the packed bed against a down flowing liquid. Air inlets are provided for flowing air to the upper portion of the bed to cool the upper portion of the bed for further condensation and particle growth within the bed.
A scrubber is also provided for removing chemical pollutants. The scrubber comprises at least two vertically separated beds containing coated packing and a monitoring means for automatically controlling selective introduction of a regenerative coating into the beds.